A.42 Willamette River, Portland, OR
McCormick & Baxter Site, OR
A.42.1 Contacts
Heidi Blischke
Groundwater Solutions
503-239-8799
Scott Manzano
503-229-6748,
A.42.2 Summary
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Environment: |
River |
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Scale: |
Full |
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Contaminants of Concern: |
PAHs, metals, creosote NAPL |
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Final Remedy: |
Removal and amended cappingTechnology which covers contaminated sediment with material to isolate the contaminants from the surrounding environment. |
A.42.3 Site Description
The McCormick and Baxter site is located on the northeast shore of the Willamette River in north Portland. The site includes 41 acres of land and 23 acres of sediments beneath the Willamette River. The primary source of contamination at this site is the historical discharges of process wastewater directly to the Willamette River, and other process wastes were dumped in several areas of the site.
McCormick and Baxter Creosoting Company operated between 1944 and 1991, treating wood products with creosote, pentachlorophenol, and inorganic (arsenic, copper, chromium, and zinc) preservative solutions. Significant concentrations of wood-treating chemicals have been found in soil and groundwater at the site and in river sediments adjacent to the site.
A.42.4 Remedial Approach
Final selected remedy: Removal and amended capping
Construction activities during the sediment capA covering over material (contaminated sediment) used to isolate the contaminants from the surrounding environment. implementation consisted of the following major components: removal of approximately 1,630 pilings, bulkhead and dock remnants, in-water debris, a derelict barge in Willamette Cove, and other Willamette Cove features; construction of a multi-layer sediment cap using sand, organophilic clayClay minerals whose surfaces have been ion exchanged with a chemical to make them oil-sorbent. Bentonite and hectorite (plate-like clays) and attapulgite and sepiolite (rod-shaped clays) are treated with oil-wetting agents during manufacturing. Quaternary fatty-acid amine is applied to the clay. Amine may be applied to dry clay during grinding or it can be applied to clay dispersed in water., and armoring; monitoring well abandonment and modification; bank re-grading; and disposal and demobilization.
The sediment cap footprint encompasses approximately 23 acres and consists of a 2-foot thick layer of sand over most of the cap footprint with a 5-foot thick layer of sand over several more highly contaminated areas. Approximately 131,000 tons of sand was placed from July 7 through October 28, 2004. Within the cap footprint were areas of known NAPL migration (such as seep areas), and the cap incorporated 600 tons of bulk organophilic clay to prevent breakthrough of the NAPL through the cap. After cap placement, apparent NAPL seeps were identified in an area outside of the organophilic clay cap as a result of gas ebullitionThe act, process, or state of bubbling up usually in a violent or sudden display.. In response to these seeps, reactive core mat containing organophilic clay were placed in these locations.
The sediment cap design incorporated different types of armoring to prevent erosion of the sand and organophilic clay layers. Articulating concrete block (ACB) mats were installed along the shore and in shallow water where erosive forces would be the greatest due to wave action. Rock armor included 6-inch-minus, 10-inch-minus, and riprap. All shallow water 10 inch-minus and ACB armoring layers were underlain with a woven geotextile fabric and 4-inch thick layer of 3-inch-minus filter rock. This fabric and rock was installed to hinder the migration of the sand through the larger and more porous armoring layer or layers.
A.42.5 Monitoring
Monitoring post cap and armoring placement identified occasional sheens around the site. Investigation showed, however, that these sheens were biological in origin and not associated with the contamination at the site (Oregon 2009). A portion of the site that included organophilic clay in the cap was also subject to significant gas ebullition. Monitoring suggested that this was coupled with reductions in organic matter content in the specific bulk organophilic clay employed in the remediationThe act or process of abating, cleaning up, containing, or removing a substance (usually hazardous or infectious) from an environment. (Reible et al. 2010). Monitoring also indicated that the specific bulk organophilic clay employed in the remediation was highly variable across the site and did not exhibit the sorptionThe process in which one substance takes up or holds another; adsorption or absorption. capacity of other commercially available organophilic clays. Despite this, the rather conservative design with 1 ft thick layers of organophilic clay as part of the cap in the active seep areas has been sufficient to ensure that no NAPL has migrated significantly into or through the cap (Reible and Lu. 2010).
RAOs/project objectives achieved? The remediation has been successful at effectively containing the contamination at the site and current monitoring shows that the site is meeting remediation objectives (USEPA 2011).
A.42.6 References
McCormick & Baxter Superfund Site, US EPA Region 10, http://yosemite.epa.gov/r10/cleanup.nsf/sites/mccormick_baxter.
Publication Date: August 2014